1. Field of the Invention
The present invention relates to an inspection method of inspecting the quality for water in an atomic reactor vessel and an apparatus therefor.
2. Description of the Prior Art
The method for inspecting the water quality in an atomic reactor is exemplified in the prior art by inserting a test piece of a predetermined shape into a reactor vessel to measure a change in the behavior of the crack growth of the test piece due to a change in the stress corrosion crack phenomenon accompanying the water quality change due to a change in the dissolved oxygen concentration. Here, examples of the defective shape detecting method of the test piece and the apparatus therefor are the technology disclosed in Japanese Patent Laid-Open No. 80104/1985.
In this prior art, the change in the water quality (in which the corrosion rate of the test piece material is increased to raise the corrosion growth rate when the dissolved oxygen concentration in pure water is increased) is detected from the change in the crack growth rate in the test piece so that the usable lifetime of the test piece is monotonously decreased with the crack growth. Especially in case the water quality is seriously changed, the crack growth rate is drastically accelerated. After the counter-measures for preventing the water quality change, the crack length is so elongated that the test piece has to be replaced soon. This raises a problem that it is difficult to accomplish a continuous inspection of one test piece for a long time (longer than at least a periodic inspection interval). In addition, the water quality inspection method using the corrosion potential is exemplified by the technology, as disclosed in Japanese Patent Laid-Open No. 75646/1988.